reanable highlighting for IPython

backport jupyter/notebook#94

https://github.com/jupyter/notebook/pull/94

IPython/html/static/notebook/js/notebook.js

@@ -135,7 +135,7 b' define(function (require) {'
         this.notebook_name_blacklist_re = /[\/\\:]/;
         this.nbformat = 4; // Increment this when changing the nbformat
         this.nbformat_minor = this.current_nbformat_minor = 0; // Increment this when changing the nbformat
-        this.codemirror_mode = 'ipython';
+        this.codemirror_mode = 'text';
         this.create_elements();
         this.bind_events();
         this.kernel_selector = null;